1. Field of the Invention
The present invention relates to a spin valve magnetic detecting element, and particularly to a magnetic detecting element capable of effectively improving a change xcex94R in resistance.
2. Description of the Related Art
FIG. 10 is a sectional view showing a conventional magnetic detecting element.
The spin valve magnetic detecting element shown in FIG. 10 comprises a multilayer film 6 comprising an antiferromagnetic layer 2, a pinned magnetic layer 3, a nonmagnetic material layer 4, and a synthetic ferrimagnetic free magnetic layer 5 including a first free magnetic sub-layer 5a, a nonmagnetic intermediate layer 5b, and a second free magnetic sub-layer 5c, which are laminated in that order from the bottom. The spin valve magnetic detecting element further comprises electrode layers 1 and 7 formed below and above the multilayer film 6, hard bias layer 8 formed on both sides of the free magnetic layer 5, insulating layers 9 formed below the respective hard bias layers 8, and insulating layers 10 formed on the respective hard bias layers 8.
The antiferromagnetic layer 2 is made of PtMn, and each of the pinned magnetic layer 3, and the first and second free magnetic sub-layers 5a and 5c of the free magnetic layer 5 is made of CoFe, the nonmagnetic intermediate layer 5b of the free magnetic layer 5 is made of Ru, the nonmagnetic material layer 4 is made of Cu, each of the hard bias layers 8 is made of a hard magnetic material such as CoPt or the like, each of the insulating layers 9 and 10 is made of alumina, and each of the electrode layers 1 and 7 is made of an electrically conductive material.
The magnetic detecting element shown in FIG. 10 is referred to as a xe2x80x9cspin valve magnetic detecting elementxe2x80x9d, for detecting a recording magnetic field from a recording medium such as a hard disk or the like.
The magnetic detecting element shown in FIG. 10 is a CPP (current perpendicular to the plane) type magnetic detecting element in which a current flows perpendicularly to the film plane of each of the layers of the multilayer film 6.
The magnetization direction of the pinned magnetic layer 3 is pinned in the Y direction shown in the drawing. For example, when the magnetic thickness (saturation magnetization Msxc3x97thickness t) of the second free magnetic sub-layer 5c is larger than that of the first free magnetic sub-layer 5a, the magnetization direction of the second free magnetic sub-layer 5c with no external magnetic field applied thereto is oriented in the track width direction (the X direction shown in the drawing) and put into a single magnetic domain state by a longitudinal bias magnetic field from each hard bias layer 8. On the other hand, the magnetization direction of the first free magnetic sub-layer 5a is oriented antiparallel to the track width direction. The magnetization direction of the whole free magnetic layer 5 coincides with the magnetization direction of the second free magnetic sub-layer 5c having a larger magnetic thickness. With an external magnetic field applied, magnetizations of the first and second free magnetic sub-layers 5a and 5c rotate while maintaining a synthetic ferrimagnetic state to change the electric resistance of the multilayer film 6. The change in the electric resistance is taken as a change in voltage or a change in current to detect the external magnetic field.
When a current flows through a magnetic material, the magnetic material has different values of resistivity for majority conduction electrons and for minority conduction electrons.
In the magnetic material, the magnetic moment of a constituent magnetic atom is mainly defined by the orbital magnetic moment and spin magnetic moment of a 3d-or 4f-orbit electron. Basically, the number of 3d-or 4f-orbit spin-up electrons is different from the number of 3d-or 4f-orbit spin-down electrons. Of the 3d- or 4f-orbit spin-up electrons and spin-down electrons, the spin of a larger number of the electrons is referred to as a xe2x80x9cmajority spinxe2x80x9d, and the spin of a smaller number of the electrons is referred to as a xe2x80x9cminority spinxe2x80x9d.
On the other hand, a current flowing through the magnetic material contains substantially the same number of spin-up and spin-down conduction electrons. Of the spin-up and spin-down conduction electrons, the conduction electrons having the same spin as the majority spin of the magnetic material are referred to as xe2x80x9cmajority conduction electronsxe2x80x9d, and the conduction electrons having the same spin as the minority spin are referred to as xe2x80x9cminority conduction electronsxe2x80x9d.
Assuming that a resistivity value of a magnetic material for the minority conduction electrons is xcfx81↓, and a resistivity value for the majority conduction electrons is xcfx81↑, a xcex2 value inherent to the magnetic material can be defined by the following relational expression:
xcfx81↓/xcfx81↑=(1+xcex2)/(1xe2x88x92xcex2)(xe2x88x921xe2x89xa6xcex2xe2x89xa61)
Namely, when the xcex2 value of the magnetic material is positive (xcex2 greater than 0), xcfx81↓ greater than xcfx81↑ is established, and thus the majority conduction electrons easily flow through the magnetic material. On the other hand, when the xcex2 value of the magnetic material is negative (xcex2 less than 0), xcfx81↓ less than xcfx81↑ is established, and thus the minority conduction electrons easily flow through the magnetic material.
In a laminate of a magnetic layer made of a magnetic material and a nonmagnetic layer made of a nonmagnetic material, an interface resistance occurs at the interface between the magnetic layer and the nonmagnetic layer.
The interface resistance also shows different values for the majority conduction electrons and the minority conduction electrons.
Assuming that the interface resistance value for the minority conduction electrons is r↓, and the interface resistance value for the majority conduction electrons is r↑, a xcex3 value inherent to a combination of a magnetic material and a nonmagnetic material can be defined by the following relational expression:
r↓/r↑=(1+xcex3)/(1xe2x88x92xcex3)(xe2x88x921xe2x89xa6xcex3xe2x89xa61)
Namely, when the xcex3 value is positive (xcex3 greater than 0), r↓ greater than r↑ is established, and thus the majority conduction electrons easily flow at the interface. On the other hand, when the y value is negative (xcex3 less than 0), r↓ less than r↑ is established, and thus the minority conduction electrons easily flow at the interface.
In the magnetic detecting element shown in FIG. 10, the pinned magnetic layer 2, and the first and second free magnetic sub-layers 5a and 5c are made of magnetic materials CoFe having the same composition. CoFe shows a positive xcex2 value. Namely, the majority conduction electrons easily flow through each of the pinned magnetic layer 2 and the first and second free magnetic sub-layers 5a and 5c. 
The nonmagnetic material layer 4 is made of Cu. Also, both the interface between the nonmagnetic material layer 4 and the pinned magnetic layer 3 and the interface between the nonmagnetic material layer 4 and the first free magnetic sub-layer 5a show positive xcex3 values.
The nonmagnetic intermediate layer 5b is made of Ru. Also, both the interface between the first free magnetic sub-layer 5a and the nonmagnetic intermediate layer 5b and the interface between the second free magnetic sub-layer 5c and the nonmagnetic intermediate layer 5b show negative xcex3 values.
FIG. 11 shows a relation between xcex2 and xcex3 values and each magnetic layer. FIG. 11 schematically shows the layers related to the magnetoresistive effect of the magnetic detecting element shown in FIG. 10. In FIG. 11, the magnetization direction of each of the pinned magnetic layer 3 and the first and second free magnetic sub-layers 5a and 5c is shown by an arrow. The majority spin of the electrons related to magnetization of a magnetic layer showing a rightward magnetization direction in the drawing is spin up, and the majority spin of the electrons related to magnetization of a magnetic layer showing a leftward magnetization direction in the drawing is spin down. Magnetization of each of the first and second free magnetic sub-layers 5a and 5c is oriented in a direction in which the resistance value of the magnetic detecting element becomes minimum.
In order to increase the change xcex94R in resistance of the magnetic detecting element, when the magnetization of the free magnetic layer 5 is oriented in the direction shown by an arrow in FIG. 11, the resistance values for the spin-up conduction electrons are preferably lower than the resistance values for the spin-down conduction elections in all magnetic layers, and the interface resistance values for the spin-up conduction electrons are preferably lower than the interface resistance values for the spin-down conduction electrons at the interfaces between the all magnetic layers and the nonmagnetic material layers (the nonmagnetic material layer 4 and the nonmagnetic intermediate layer 5b). Alternatively, the resistance values for the spin-down conduction electrons are preferably lower than the resistance values for the spin-up conduction elections in all magnetic layers, and the interface resistance values for the spin-down conduction electrons are preferably lower than the interface resistance values for the spin-up conduction electrons at the interfaces between the all magnetic layers and the nonmagnetic material layers (the nonmagnetic material layer 4 and the nonmagnetic intermediate layer 5b).
Referring to FIG. 11, in each of the pinned magnetic layer 3 and the first free magnetic sub-layer 5a in which the majority spin is spin up, and xcex2 greater than 0, the resistance value for the spin-up conduction electrons is low, while in the second free magnetic sub-layer 5c in which the majority spin is spin down, and xcex2 greater than 0, the resistance value for the spin-up conduction electrons is high.
Also, at the interface between the nonmagnetic material layer 4 and the pinned magnetic layer 3, the interface between the nonmagnetic material layer 4 and the first free magnetic sub-layer 5a, and the interface between the nonmagnetic intermediate layer 5b and the second free magnetic sub-layer 5c, the interface resistance for the spin-up conduction electrons is lower than that for the spin-down conduction electrons. However, at the interface between the first free magnetic sub-layer 5a and the nonmagnetic intermediate layer 5b, the interface resistance for the spin-up conduction electrons is higher than that for the spin-down conduction electrons.
In this way, the conventional magnetic detecting element has a low efficiency of flow control of conduction electrons.
The present invention has bees achieved for solving the problem of the above-described conventional magnetic detecting element, and an object of the present invention is to provide a magnetic detecting element capable of increasing a difference between ease of a conduction electron flow under a low resistance condition and ease of a conduction electron flow under a high resistance condition to increase a change AR in resistance.
A magnetic detecting element of the present invention comprises a multilayer film comprising an antiferromagnetic layer, a pinned magnetic layer, a nonmagnetic material layer and a free magnetic layer, which are laminated in that order, the free magnetic layer including a first free magnetic sub-layer and a second free magnetic sub-layer laminated on the first free magnetic sub-layer with a nonmagnetic intermediate layer provided therebetween, wherein the xcex2 value of a magnetic material constituting the first free magnetic sub-layer has a positive or negative sign which is the same as that of the pinned magnetic layer and different from that of the second free magnetic sub-layer, or the xcex2 value of a magnetic material constituting the second free magnetic sub-layer has a positive or negative sign which is the same as that of the pinned magnetic layer and different from that of the first free magnetic sub-layer.
However, the xcex2 value is inherent to a magnetic material satisfying the relational expression, xcfx81↓/xcfx81↑=(1+xcex2)/(1xe2x88x92xcex2)(xe2x88x921xe2x89xa6xcex2xe2x89xa61) (wherein xcfx81↓ is a resistivity value for the minority conduction electrons, and xcfx81↑ is a resistivity value for the majority conduction electrons).
A magnetic detecting element of the present invention comprises a multilayer film comprising an antiferromagnetic layer, a pinned magnetic layer, a nonmagnetic material layer and a free magnetic layer, which are laminated in that order, the pinned magnetic layer including a first pinned magnetic sub-layer and a second pinned magnetic sub-layer laminated on the first pinned magnetic sub-layer with a nonmagnetic intermediate layer provided therebetween, wherein the xcex2 value of a magnetic material constituting the second pinned magnetic sub-layer has a positive or negative sign which is the same as that of the free magnetic layer and different from that of the first pinned magnetic sub-layer, or the xcex2 value of a magnetic material constituting the first pinned magnetic sub-layer has a positive or negative sign which is the same as that of the free magnetic layer and different from that of the second pinned magnetic sub-layer.
A magnetic detecting element of the present invention comprises a multilayer film comprising an antiferromagnetic layer, a pinned magnetic layer, a nonmagnetic material layer and a free magnetic layer, which are laminated in that order, the free magnetic layer including a first free magnetic sub-layer, a nonmagnetic intermediate layer, a second free magnetic sub-layer, a nonmagnetic intermediate layer and a third free magnetic sub-layer, which are laminated in that order, wherein the xcex2 value of a magnetic material constituting the first free magnetic sub-layer has a positive or negative sign which is the same as those of the third free magnetic sub-layer and the pinned magnetic layer and different from that of the second free magnetic sub-layer, or the xcex2 value of a magnetic material constituting the second free magnetic sub-layer has a positive or negative sign which is the same as that of the pinned magnetic layer and different from those of the first free magnetic sub-layer and the third free magnetic sub-layer.
In the present invention, if the xcex2 value of the magnetic material constituting each of the free magnetic layer (the first free magnetic sub-layer, the second free magnetic sub-layer and the third free magnetic sub-layer) and the pinned magnetic layer (the first pinned magnetic sub-layer and the second pinned magnetic sub-layer) (these layers are simply referred to as the xe2x80x9cmagnetic layersxe2x80x9d) is defined, when magnetization of the free magnetic layer is changed to minimize the resistance value, the resistance values for the spin-up conduction electrons are lower than the resistance values for the spin-down conduction electrons in all magnetic layers, or the resistance values for the spin-down conduction electrons are lower than the resistance values for the spin-up conduction electrons in all magnetic layers, thereby increasing the change xcex94R in resistance of the magnetic detecting element.
In the present invention, the xcex3 value at the interface between the first free magnetic sub-layer, the second free magnetic sub-layer, the third free magnetic sub-layer, the first pinned magnetic sub-layer or the second pinned magnetic sub-layer and the nonmagnetic intermediate layer or the nonmagnetic intermediate layer preferably has the same positive or negative sign as that of the xcex2 value of the magnetic layer in contact with the interface.
However, the xcex3 value is inherent to an interface satisfying the relational expression, r↓/r↑=(1+xcex3)/(1xe2x88x92xcex3)(xe2x88x921xe2x89xa6xcex3xe2x89xa61) (wherein r↓ is the interface resistance value for the minority conduction electrons, and r↑ is the interface resistance value for the majority conduction electrons).
In the present invention, if the xcex3 value is defined, when magnetization of the free magnetic layer of the spin valve magnetic detecting element is changed to minimize the resistance value, the interface resistance values for the spin-up conduction electrons are lower than the interface resistance values for the spin-down conduction electrons at the interfaces between all magnetic layers and the nonmagnetic material layers (the nonmagnetic material layer and the nonmagnetic intermediate layers), or the interface resistance values for the spin-down conduction electrons are lower than the interface resistance values for the spin-up conduction electrons at all interfaces, thereby increasing the change xcex94R in resistance of the magnetic detecting element.
In order to define the xcex3 value as described above, in some cases, the positive or negative sign of the xcex3 value at the interface between the magnetic layer and the top of the nonmagnetic material layer or the nonmagnetic intermediate layer must be differentiated from that at the interface between the magnetic layer and the bottom of the nonmagnetic material layer or the nonmagnetic intermediate layer. However, in the present invention, the nonmagnetic material layer and/or the nonmagnetic intermediate layer is formed in a two-layer structure comprising different nonmagnetic materials, for solving the problem of this necessity.
A magnetic detecting element of the present invention comprises a multilayer film comprising an antiferromagnetic layer, a pinned magnetic layer, a nonmagnetic material layer and a free magnetic layer, which are laminated in that order, the free magnetic layer including a first free magnetic sub-layer and a second free pinned magnetic layer laminated on the first free magnetic sub-layer with a nonmagnetic intermediate layer provided therebetween, wherein assuming that a NiX alloy (wherein X is an element selected from Co, Fe, Mn, Zr, Hf, Cu and Au), a CoT alloy (wherein T is an element selected from Fe, Zr, Ta and Hf,), an FeZ alloy (wherein Z is an element selected from Ni, Co, Rh, Pt, Ir, Be, Al, Si, Ga and Ge), or a Coxe2x80x94Mn-D alloy (wherein D is an element selected from Al, Ga, Si, Ge and Sn) is an alloy belonging to an A group, and a NiM alloy (wherein M is an element selected from Cr, Rh, Ru, Mo, Nb, Pt, Ir, Os, Re, W and Ta), a CoQ alloy (wherein Q is an element selected from Mn, Cr, Ru, Mo, Ir, Os, Re and W), or an FeA alloy (wherein A is an element selected from Mn, Cr, V, Ti, Ru, Mo, Os, Re and W) is an alloy belonging to a B group, a magnetic material constituting the first free magnetic sub-layer comprises an alloy belonging to the A or B group which is the same as that of the pinned magnetic layer and different from that of the second free magnetic sub-layer, or a magnetic material constituting the second free magnetic sub-layer comprises an alloy belonging to the A or B group which is the same as that of the pinned magnetic layer and different from that of the first free magnetic sub-layer.
In the magnetic detecting element of the present invention, the pinned magnetic layer may comprise a first pinned magnetic sub-layer, and a second pinned magnetic sub-layer laminated on the first pinned magnetic sub-layer with a nonmagnetic intermediate layer provided therebetween, wherein a magnetic material constituting the second pinned magnetic sub-layer comprises an alloy belonging to the A or B group which is the same as that of the free magnetic layer and different from that of the first pinned magnetic sub-layer, or a magnetic material constituting the first pinned magnetic sub-layer comprises an alloy belonging to the A or B group which is the same as that of the free magnetic layer and different from that of the second pinned magnetic sub-layer.
In the magnetic detecting element of the present invention, the free magnetic layer may comprise a first free magnetic sub-layer, a nonmagnetic intermediate layer, a second free magnetic sub-layer, a nonmagnetic intermediate layer and a third free magnetic sub-layer, which are laminated in that order, wherein a magnetic material constituting the first free magnetic sub-layer comprises an alloy belonging to the A or B group which is the same as those of the third free magnetic sub-layer and the pinned magnetic layer and different from that of the second free magnetic sub-layer, or a magnetic material constituting the first free magnetic sub-layer comprises an alloy belonging to the A or B group which is the same as that of the third free magnetic sub-layer and different from those of the second free magnetic sub-layer and the pinned magnetic layer.
In the spin valve magnetic detecting element of the present invention, if the magnetic material constituting each of the magnetic layers is defined, when magnetization of the free magnetic layer is changed to minimize the resistance value, the resistance values for the spin-up conduction electrons are lower than the resistance values for the spin-down conduction electrons in all magnetic layers, or the resistance values for the spin-down conduction electrons are lower than the resistance values for the spin-up conduction electrons in all magnetic layers, thereby increasing the change xcex94R in resistance of the magnetic detecting element.
In the present invention, at least one of the nonmagnetic material layer and the nonmagnetic intermediate layer comprises a laminated film of a Cu layer and a Cr layer. When the laminated film is held between a magnetic layer made of an alloy belonging to the A group and a magnetic layer made of an alloy belonging to the B group, the resistance values for the spin-up conduction electrons are lower than the resistance values for the spin-down conduction electrons at all interfaces, or the resistance values for the spin-down conduction electrons are lower than the resistance values for the spin-up conduction electrons at all interfaces, thereby increasing the change xcex94R in resistance of the magnetic detecting element.
In the present invention, even when the thicknesses of all of the nonmagnetic intermediate layer, the first free magnetic sub-layer and the nonmagnetic material layer are smaller than the spin diffusion lengths of the materials constituting the respective layers, the change xcex94R in resistance of the magnetic detecting element can be increased.
Also, even when the thicknesses of all of the free magnetic layer, the nonmagnetic material layer, the second pinned magnetic sub-layer and the nonmagnetic intermediate material layer are smaller than the spin diffusion lengths of the materials constituting the respective layers, the change xcex94R in resistance of the magnetic detecting element can be increased.
Furthermore, even when the thicknesses of all of the nonmagnetic intermediate layer, the second free magnetic sub-layer, the nonmagnetic material layer, the first fee magnetic layer and the nonmagnetic material layer are smaller than the spin diffusion lengths of the materials constituting the respective layers, the change xcex94R in resistance of the magnetic detecting element can be increased.